432 SCIENTIFIC THOUGHT. 



it were the inner atmosphere which any large assembly 

 of living units must necessarily create for itself. All 

 larger organisms are complex societies of living units 

 which depend not only on the external but also on the 

 internal medium which bathes them. It was one of 

 Claude Bernard's happiest generalisations to look upon 

 the blood, not as a living tissue but as a means of com- 

 munication of the living tissues of the organism, as 

 39. an internal medium which bears the same relation to 



The 



"internal the constituent tissues that the external medium, the 



medium." 



atmosphere, does to the whole body. 



One of the principal functions of this artificial medium 

 or atmosphere which the larger organisms possess, create 

 and maintain for themselves during their life, is to 

 enable a particular elementary substance to get access 

 to every living cell or tissue of the organism. This 

 substance is oxygen, without which the continuance 

 of life in the higher organisms seems impossible. 

 That life is a process of combustion is accordingly a 



possess ' ' un milieu interieur per- I organique circulant qui entoure et 

 fectionne " (p. 104). But they ' baigne tous les elements anatom- 



begin their existence as beings 

 with an oscillating life when they 

 are in the form of eggs. Of the 

 vie constantc ou libre Claude Bernard 

 says : " Je crois avoir le premier 

 insiste sur cette idee qu'il y a pour 

 1'aniinal reellemeut deux milieux ; 



iques des tissus ; c'est la lymphe 

 ou le plasma, la partie liquide du 

 sang qui chez les animauxsuperieurs, 

 pe"netre les tissus et constitue 

 I'ensemble de tous les liquides in- 

 terstitials, expression de toutes les 

 nutritions locales, source et cou- 



un milieu exterieur dans lequel est j fluent de tous les echanges ele- 

 place 1'organisme, et un milieu mentaires. Un organisme complexe 

 interieur dans lequel vivent les 



elements des tissus. L'existence 

 de 1'etre se passe, non pas dans le 



doit etre considere comme une 

 reunion d'Stres simples qui sont 

 les elements anatomiques et qui 



milieu exteYieur, air atmospherique viveut dans le milieu liquide in- 

 pour 1'etre aerien, eau douce ou ' terieur. La fixite du milieu in- 

 salee pour les animaux aquatiques, , te'rieur est la condition de la vie 



mais dans le milieu liquide 

 terieur forms' par le liquide 



libre independante" (p. 113). 



